Conventionally, a III-nitride semiconductors made of compounds in which N is combined with Group III elements such as Al, Ga, In, etc. are used as materials for light-emitting devices emitting blue to deep ultraviolet light. III-nitride semiconductors made of high-Al-content AlGaN are particularly used for ultraviolet light-emitting devices emitting light at a wavelength of 340 nm or less, or deep ultraviolet light light-emitting devices (DUV-LED) emitting light at a wavelength of 300 nm or less.
Here, with reference to FIG. 1, a III nitride semiconductor light-emitting device 100 having a typical lateral structure in conventional techniques will be described. The III nitride semiconductor light-emitting device 100 has a substrate 1, a buffer 2, an n-type III nitride semiconductor layer 3, a light emitting layer 4, and a p-type III nitride semiconductor layer 5 in this order. Subsequently, the light emitting layer 4 and the p-type III nitride semiconductor layer 5 are partially removed while the n-type III nitride semiconductor layer 3 is partly removed to provide an exposed portion. The removal is performed for example by etching. An n-type ohmic electrode 6a and a pad electrode 7a are sequentially formed on the surface of the exposed portion. Further, a p-type ohmic electrode 6b and a pad electrode 7b are also formed sequentially on the surface of the p-type III nitride semiconductor layer 5.
With respect to a III nitride semiconductor light-emitting device having such a lateral structure, JP 2003-309285 A (PTL 1) discloses a method of producing a Group III nitride compound semiconductor device having at least an n-type layer and a p-type layer on a substrate, wherein an n-electrode and a p-electrode are provided on a surface side of the device, the n-electrode is formed on a portion of the n-type layer exposed by etching, the p-type layer is doped with a p-type impurity, the resistance of the p-type layer is made low by irradiation with an electron beam, and an end face formed by etching after the electron beam irradiation is acidized.
Further, JP 2010-056459 A (PTL 2) discloses a method of producing a light-emitting device, comprising the steps of: forming, on a first main surface of a single crystal substrate of a III nitride semiconductor having the first main surface exhibiting Group-III polarity and a second main surface exhibiting N polarity, an optical semiconductor portion by stacking a first conductivity type III nitride semiconductor layer, a light emitting layer made of a III nitride semiconductor, and a second conductivity type III nitride semiconductor layer; forming a polarity reversing layer that converts N polarity into Group-III polarity on the second main surface by epitaxial growth; and forming a pyramidal III nitride semiconductor on the polarity reversing layer by epitaxial growth so that the crystal planes grown constitute the lateral faces of the pyramid.